I'm hoping to buy a double bass pedal and I was wondering if the pedal comes with a hi-hat drop clutch, and if not, if a hi-hat drop clutch is necessary. I'd like to be able to play on the hi-hat while also playing double bass. If a drop clutch is necessary, please refer me to a good one (preferably on Musican's Friend).

It depends on the music. Some drummers leave the standard clutch because they can switch in between tunes. Some drummers play tunes where the drummer switches to opening and closing hats.
I would say get one because they are inexpensive and you will always find a use for it.

It depends on your style as stated, Keith Moon did away with hid hi hats altogether. I went through several before settling on the Pearl http://www.musiciansfriend.com/drums...0p-drop-clutch . Several reasons, it does not mar your hi hat rod the way the others do and it has never failed, I like the release better than the others as well and the rubber instead of felts make the hats sound better IMO. I got new hats and decided to keep my old ones and use them on an X-hat stand and leave them a little open. I kept my drop clutch and still use it occasionally. Its really all about person preference. Good luck.

I had one when I used to mess around on my old iron cobra double bass pedal. They're kinda tricky - I feel like it would be easier just to use a regular clutch and just ride on a cymbal or crash when doing tasty double bass fills

Unless your doing constant double bass pedaling and you need to have the closed hh sound - i would just get used to using a regular one.

Depends on how open you leave your hats at the rest position to start with . If you leave them pretty close together, then you won't need it. When you plsy double bass, you can hit then and have that sizzle effect of half open hihats. If you like them opened more (like I do) , you'll need it . You won't be able to sizzle but will have them close .

I agree that you can get away without having one. If you keep your hats barely touching you'll get that sloshy sound.

I have one and use it, but don't effectively use it. I end up going on the ride or crash during constant lrlrlrlr beats. I need to remember to hit the release lever if riding the hat since my hats are a little open. I like getting the occassional hihat "bark" in when you hit open hats and quickly close them.

Dixon's Inventor Series Drop Clutch is the state of the art in hi hat drop clutches

+1
I bought that one some 2 years ago, when it was still branded as a Billdidit (Canadian) product. Works great! I still like the idea to have a regular clutch on my 2nd hihat, just in case. But for double bass stuff the Dixon/Billdidit clutch is as good as it gets.